The present invention is directed to a method identifying a risk for a thrombogenic disorder including, without limitation, atrial fibrillation, stroke, prolonged intermitted neurological deficit (PRIND), transitory ischemic attack (TIA), atherosclerotic cerebrovascular disease (CVD) and/or coronary heart disease, as well as to a method for selecting patients with a risk for a thrombogenic disorder, to a method for identifying a pharmaceutical for the therapy or prophylaxis of a thrombogenic disorder as well as to a method for producing a medicament and a diagnostic by employing the TAFI-Ile347 polymorphism.
The Thrombin-Activable Fibirinolysis Inhibitor (TAFI) is a known plasma zymogen synthesized in the liver as a prepropeptide consisting of 423 amino acids with a molecular weight of 55 kDa (FIG. 1). The prepropeptide contains a 22 amino acids long signal peptide (amino acids No. 1-22), a 92 amino acids long activation peptide and a 309 amino acids long catalytic domain. The nucleic acid sequence contains 1723 nucleotides (FIG. 2). The protein sequence accession number (NCBI protein database) of TAFI is NP—001863, the nucleotide sequence accession number (NCBI nucleotide database) is NM—001872 and the accession number for TAFI information in OMIM (Online Mendelian Inheritance in Man™) is 603101.
TAFI is activated by thrombin, plasmin or the thrombin/thrombomodulin complex. After processing, TAFI attenuates clot lysis by removing lysine residues from a fibrin clot. Activated and processed TAFI is unstable at 37° C. and has a half-life of about 8 minutes. Therefore, TAFI plays a central role in homeostasis where it functions as a potent fibrinolysis inhibitor. The human TAFI gene has been mapped to chromosome 13q14.11. It consists of 11 exons and spans a genomic region of about 48 kb in length (Boffa et al. (1999) Biochemistry, 38, 6547-6558).
Genetic analyses of the TAFI gene in humans revealed several variable nucleotides (SNPs, Single Nucleotide Polymorphisms) in the promoter and the coding region. For SNPs in the promoter region of the TAFI gene it has been shown, that some of these polymorphisms are associated with altered TAFI protein levels in the blood (Franco et al. (2001) Haematologica, 86, 510-517; Henry et al. (2001) Blood, vol. 97, no. 7, 2053-2058).
Recently two SNPs have been identified in the coding region of the TAFI gene leading to an amino acid exchange in the corresponding TAFI protein, these polymorphism are T169A (T=Threonine (Thr) at position 169 to A=Alanine (Ala)) and T347I (Threonine at position 347 to I=Isoleucine (Ile)). The TAFI-Ile347 variant seems to display an extended half-life from 8 minutes to 15 minutes and seems to exhibit an enhanced antifibrinolytic potential of 60% (Brouwers et al. (2001) Blood, vol. 98, no. 6, 1992-1993; Schneider et al. (2001) J. Biological Chemistry, vol. 277, no. 2, 1021-1030) under the tested in vitro conditions. Variations at position 169 of the TAFI protein do not seem to have any effect on the antifibrinolytic potential of TAFI (Schneider et al. (2001) supra). However, currently no data are available about the clinical effects, if any, of the described polymorphisms including the TAFI-Ile347 variant for thrombogenic or other disorders.